Transpose the prescription

-0.75DS/-3.25DCx30 to the toric form with a capstan-form surface which has a +2.50D base curve

I have had a look at that website but still struggling

http://www.optiboard.com/forums/showthread.php/18768-Need-Help-For-Ophthalmic-Question!

and page 30 from
http://www.optometry.co.uk/uploads/articles/949e0d09ac024c2edb6d55bad5da4d11_jalie20050225.pdf

Is the answer +2.50dcx120/+5.75dcx120?

Or is it (-6.50dcx30/-3.25dcx120)/2.5ds?

To transpose the prescription -0.75DS/-3.25DCx30 to the toric form with a capstan-form surface, you need to follow a specific calculation process.

Here are the steps you can take:

Step 1: Convert the prescription to its equivalent spherical form.
- The -0.75DS means there is a spherical component of -0.75 diopters.

Step 2: Determine the back vertex power (BVP) of the required toric lens.
- The BVP is calculated by adding the spherical component (-0.75D) to the base curve (+2.50D).
- BVP = -0.75D + 2.50D = +1.75D

Step 3: Determine the cylinder power for each meridian.
- The -3.25DC means there is a cylinder component of -3.25 diopters at a specific axis.
- Since the capstan-form surface uses a cylinder power of 3.00 diopters, we need to adjust the cylinder power accordingly.
- The difference between -3.25D and 3.00D is 6.25D. So, we need to reduce the cylinder power by 6.25 diopters.

Step 4: Determine the axis for the cylinder component.
- The axis of the cylinder component is given as 30 degrees.

Step 5: Write down the transposed prescription in toric form.
- The transposed prescription with the capstan-form surface would be:
+1.75DS/-0.25DCx30

Please note that this is a general guide to transpose a prescription to a toric form with a specific surface type. However, for accurate and precise calculations, it is always recommended to consult with a qualified optician or eye care professional.